Saturable transformer device



May 11, 1954 A. BENNETT 2,678,419

SATURABLE TRANSFORMER DEVICE Filed Sept. 30, 1946 INVENTOR 1/5. "IL FREDBENNETT A i TORNEY Patented May 11, 1954 SATURABLE TRANSFORMER DEXICEAlfred Bennett, New York, N. Y., 'assignor to Bendix AviationCorporation, Teterboro, N. J a corporation of Delaware ApplicationSeptember 30, 1946, Serial No. 700,234

2 Claims. 1

The present invention relates generally to electrical current flowcontrol apparatus and more particularly to apparatus of a characteradapted for developing, in response to a direct current control signal,a proportional alternating current signal.

Heretofore, in applications where it has been desired to operate analternating current control system in accordance with a controllingdirect current signal, involved networks including thermionic tubes wererequired. The present invention contemplates the provision of a simplearrangement obviating the past requirement for vacuum tubes, etc, whichin response to a direct current control signal, such as that provided bya radio receiver carried by an aircraft and constituting a part of ablind landing system including a localizer and glidebeam path control,for example, will develop a proportional and properly phased alternatingcurrent signal for operating given craft surfaces in accordance with thereceived radio signal or signals.

An object of the present invention, therefore, is to provide a novelelectrical inverter which is adapted for developing an alternatingcurrent signal proportional to a direct current signal.

Another object is to provide a novel electrical device which is adaptedfor developing a workable alternating current signal from an extremelyweak direct current signal without the necessity for the use of vacuumtubes or other amplifiers.

A further object is to provide a novel and simplified electrical currentflow control device which will provide a workable alternating currentsignal in response to a relatively weak direct 1 current signal whosephase will be determined by the direction of flow of the direct currentsignal.

Another object of the present inventionis to provide a novel and simpleelectrical device adapted for use wherever a workable, amplified andproperly phased alternating current signal is required in response to arelatively weak direct current signal.

The above and other objects and advantages of the invention will appearmore fully hereinafter from aconsideration of the detailed descriptionwhich follows, taken together with the accompanying drawing wherein oneembodiment of the invention is illustrated. It is to be expresslyunderstood, however, that the drawing is for the purpose of illustrationand description only, and is not designed as a definition of the limitsof the invention.

In the drawings, wherein like reference characters refer to like partsthroughout the several views,

Figure 1 is a schematic diagram showing the various electrical circuitsof the novel apparatus constituting the subject matter of the presentinvention;

Figure 2 is a detail view, showing the aiding relation at a given timeof the fluxes in the center leg of one of the cores of Figure 1; and,

Figure 3 is a detail view, similar to that of Figure 2, showing theopposing relation during the time under consideration of the fluxes inthe center leg of the other of the cores of Figure 1.

Referring now to the drawing for a more detailed description of thenovel electrical apparatus constituting the subject matter of thepresent invention, the latter is shown in Figure 1 as comprising a pairof similar cores I0 and H formed of magnetically permeable material suchas Permalloy or Mumetal, for example, core H! being provided with acenter leg [2 and spaced outer legs [3 and I4 and core ll beingsimilarly provided with a center leg [5 and spaced outer legs I6 and I1.

Primary windings l8, iii, 20 and 2| are provided for cores [0 and H,windings I8 and I9 being arranged on outer legs l3 and i4, respectively,of core Ii) and windings 20 and 2| being arranged on outer legs IS andI1, respectively, of core Ii. One end of winding 58 is connected by wayof a conductor 22 with one side of. a suitable source of alternatingcurrent (not shown) while the opposite end of winding it connects by wayof a conductor 23 with one end of primary winding 19. The opposite endof the latter winding, in turn, connects with. one end of primarywinding 20"by way of a conductor 24 while the opposite end of winding 28connects by way of a conductor '25 with one end of winding 2!, theopposite end of the latter being connected by way of a conductor 25 withthe opposite end of the alternating current source.

It will be apparent that primary windings I8, I9, 29 and 2! are allconnected in series aiding relation with each other and with the sourceof alternating current supplying the primary windings so that windingsl8 and I9 aid each other in circulating flux, indicated by the arrows 2?in Figure 1., around the long circuit of core 1-0 but oppose each otherin the center leg [2 while windings 2i) and 2| will aid each other incirculating flux, indicated by the arrows 28, around the long circuit ofcore H but oppose each other in the center leg l5.

Secondary windings 29, 30, 3| and 32 are further provided on both coresIt and II and are so arranged that they are normally unaffected by thefluxes traversing the long circuits of both cores, i. e., no signal willappear at the secondary output. To this end, secondary windings 29 and30 arranged on legs l3 and (4, respectively, of core it are connected inseries by way of a conductor 33 while windings 3i and 32 arranged onlegs l8 and H, respectively, of core H are connected in series by way ofa conductor 34, the free end of winding 29 being connected by way of aconductor 35 with one side of a device 36 responsive to an alternatingcurrent signal and the free end of winding 3! being connected withthe-opposite side of the signal responsive device by way of a conductor3'1. While the secondary windings of each pair are connected with oneanother in series aiding relation, the pair 29 and 3G is connected inseries opposing relation with the pair 3! and 32, this beingaccomplished through a conductor 38 connected to the free end of winding30 of the first pair of windings and the free end of winding 32 of thesecond pair of windings. Thus, for any signal appearing at secondarywindings ill and 30 due to current flow in primary windings l8 and IS anequal and opposits signal will appear at secondary windings 3| and 32due to current flow in primary windings 2d and 25 with the net resultthat no signal will be provided by output conductors 35 and 3'! todevice 36.

Direct current control windings in the form of coils 39 and 4B are,furthermore, provided on center legs l2 and i5, respectivel of cores l8and H and are interconnected with each other in series relation by wayof a conductor 41 and with a direct current signal generator 42 by wayof conductors ll and 44. With the arrangement thus far described,notwithstanding the amplitude or the direction of the D. C. signaldeveloped by generator 42, both cores will have fluxes threading thecenter legs thereof due to current flow in the control coils which areof equal intensity so that the balance of the electrical system isunchanged and no signal will appear at output leads 35 and 31.

In order that workable and properly phased alternating current signalmay be available at secondary outputs 35 and 31 to energize device 36 inresponse to a relatively weak direct current control signal applied tocoils 39 and 40, a second pair of direct current biasing controlwindings in the form of coils 45 and 46 are pro vided on center legs l2and 45, respectively, of cores ill and H, which are interconnected byway of a conductor 4? in series opposing relation, the free end of coil65 being connected to one side of a suitable source of D. C. current,such as a battery 48, for example, by way of a conductor 49 the free endof coil 46 being connected to the opposite side of the battery by way ofa conductor fill. Although coils 45 and 46 have been described as beingconnected in series opposed relation, it is to be understood that theycould be connected in series aiding relation as well, in which eventcontrol coils 39 and would. be connected in series opposed relation.Whichever arrangement is selected the ultimate result will be the same.

Assuming D. C. coils and 45 to have been connected in series opposedrelation in which event control coils 39 and 4B are in series aidingrelation and with no D. C. signal applied to the latter coils. magneticflux will flow in center leg I2 of core It due to D. C. current in coil45 in the direction indicated by arrow 5| in Figure 2 while magneticflux the center leg l5 of core H due to D. C. current in coil 46 willflow in the opposite direction as indicated by arrow 52 in Figure 3.While these fluxes are in opposing relation in the two center legs ofthe cores, both cores are saturated with a similar amount so that thesystem is undisturbed and no signal will appear at device 36. It willnow be readily apparent that the direction of the fluxes designated byarrows 5| and 52 will be determined by the manner that coils 45 and 46are connected to D. C. source 48.

Assuming, further, that a direct current signal is developed bygenerator 42 to flow within control coils 38 and 4 additional fluxeswill be developed in both center legs to, in one case, aid the fluxdeveloped by the other D. C. coil in one of the center legs of one ofthe cores and to oppose the flux developed by the other D. C. coil inthe other center leg of the other of the cores. For example, as shown inFigure 2, the flux resulting from current flow in control coil 39 willbe in the direction indicated by the arrow 53 to aid the flux 5! due tocurrent flow in coil 45 and thus saturate core It to make core I!) andits windings l3, l9 and 29, 30 a poor transformer while the fluxresulting from current flow in control coil 49 will be in the directionindicated by the arrow 54 to oppose the flux 52 due to current flow incoil 4G to neutralize the effect of the latter fluxes produced bycurrent flow in coils 4i! and it to thereby make core H and itsassociated windings 2t, 21 and 31, 3?. a good transformer. As a result,the electrical system is unbalanced and an alternating current flows insecondary windings 29, 30, Si and 32 to energize device 36.

The relation of the magnetic fluxes illustrated in Figures 2 and 3 ofthe drawing is that due to direct current flow in one direction withincontrol windings 39 and 40 as a result of which an A. C. signal isavailable at secondary outputs 35 and 37. It will now be apparent thatfor a reversal in the direction of current flow in control coils 39 and40 developed by generator 42, the ilux 53 of Figure 2 will be reversedto oppose the flux in center leg [2 due to current flow in coil 45 andthereby make core in and its. associated primary and secondary windingsa good transformer while the flux 54 of Figure 3 will be reversed to aidthe flux in center leg 15 due to current flow in coil 46 and therebymake core II and its associated primary and secondary windings a poortransformer. The electrical system is, thus, again unbalanced and analternating current flows in the secondary windings which issubstantially out of phase with the current flow induced in the samewindings by the direction of current flow in control coils 39 and 40first considered above.

It will now be apparent to those skilled in the art that a novelelectrical device has been provided which is adapted for developing aworkable, amplified and properly phased alternating current signal froman extremely weak direct current signal without the necessity for theuse of vacuum tubes or other amplifiers.

Although but one embodiment of the invention has been illustrated anddescribed, various changes and modifications in the form and relativearrangement of parts, which will now appear to those skilled in the art,may be made without departing from the scope of the invention. Referenceis therefore to be had to the appended claims for a definition of thelimits of the invention.

I claim:

1. An inverter of the kind described comprising a pair of core membersof magnetically permeable material, a primary Winding on each of saidcore members adapted to be energized by an alternating current source, asecondary winding on each of said core members connected independentlyof said alternating current source, a biasing winding on each of saidcore members adapted to be energized by a direct current sourceindependently of said alternating current source and independent- 1y ofsaid secondary windings to produce a unidirectional magnetic flux ineach of said cores, a signal source for producing direct current signalsindependently of the alternating current source and independently of thesecondary windings, a control winding on each of said cores connected tosaid signal source and arranged to increase the unidirectional magneticflux in one of said core members and to decrease the unidirectionalmagnetic flux in the other core member in response to the direct currentsignals so that alternating currents corresponding in phase to thepolarity of the direct current signals are induced in said secondarywindings, and means con ected to said secondary windings and controlledby said signal source and responsive solely to the alternating currentsinduced in said secondary windings.

2. An inverter of the kind described comprising a pair of core membersof magnetically permeable material each having a central leg and a pairof spaced outer legs, primary windings on the outer legs of said coremembers adapted to be energized by an alternating current source,secondary windings on the outer legs of said core member connectedindependently of said alternating current source so that no signal isinduced in said secondary windings solely in re sponse to energizationof said primary windings, biasing windings adapted to be connected to adirect current source independently of the alternating current sourceand independently of said secondary windings for producing aunidirectional magnetic flux in each of said core mem bers, a signalsource adapted to produce direct current signals independently of thealternating current source and independently of said secondary windings,control windings on the central legs of said core members connected tosaid direct current signal source to decrease the unidirectionalmagnetic fiux in one of said core members and to increase theunidirectional magnetic flux in the other core member in response todirect current signals so that alternating cur rents are induced in saidsecondary windings corresponding in phase to the polarity of the directcurrent signals, and mean connected to said secondary windings andcontrolled by said signal source and responsive solely to thealternating currents induced in said secondary windings.

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